Establishment and validity verification of the hot processing map of a Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy with a lamellar microstructure

The hot compression test of a Ti-47.5Al-2.5 V-1.0Cr-0.2Zr alloy was carried out at 1050–1200 °C and a strain rate of 0.001–1 s−1 by a Gleeble3800 thermal simulation testing machine. The hot processing maps at the true strains of 0.2, 0.4, 0.6, and 0.8 were established, and the optimal thermal processing parameter region and the instability region were determined. The microstructures corresponding to different regions of the processing maps were systematically studied, and the validity of the established processing maps were verified. The results indicated that when the true strain is 0.8, the optimal hot working parameter region are 1132–1185 °C and 0.001–0.002 s−1, respectively. The instability region are 1050–1125 °C/0.04–1 s−1 and 1125–1200 °C/0.7–1 s−1, respectively. The corresponding microstructures were lamellar microstructures with a bending and twisting deformation. At the same time, the instability phenomena, such as micro-cracks and voids, were found, and a large number of dislocation pile-ups appeared in the lamellar crystals. The dynamic recrystallization (DRX) degree of the microstructures corresponding to the optimal hot working parameter region is relatively complete, and the recrystallized grain size is relatively uniform. There is almost no residual lamellar microstructure, and no micro-cracks were found. The microstructures in the optimal hot working condition is obviously better than that in the instability region. The thermal processing safety region obtained in this work is authentic, and the processing map has a certain instructive role in the choice of thermal processing parameters.